Fucose is one of the so-called rare monosaccharides. It is found in a wide variety of natural products from many different sources in both D- and L-forms. Mammalian cells can make fucosylated glycans, such as ABO blood group antigens and several human milk oligosaccharides. There is fucose in eggs of sea urchins and in frog spawn. Fucose is present in polysaccharides from plants such as seaweed (in the form of fucoidan, sulphated fucose polymer); gum tragacanth, potato, kiwi fruit, soybean, winged bean varieties, canola, etc. In plants, fucose is typically associated with plant polysaccharides, which are often highly branched structures having L-fucopyranosyl units either at the ends of or within the polysaccharide chains. Both N- and O-glycosyl chains of human or animal glycoproteins can contain fucose bound to the termini of the carbohydrate chains. Furthermore, extracellular polysaccharides from various bacteria, fungi and micro-algae also contain fucose. The fucosylation process in all natural living cells has two common features: it is mediated by a fucosyl transferase enzyme, which carries the fucosyl residue to an appropriate acceptor; and it forms an activated fucose nucleotide, i.e., GDP-fucose, not fucose in free form.
Interest in fucose, particularly L-fucose, in free form has recently increased because of its potential usefulness in treating various diseases, inflammatory conditions and disorders relating to the human immune system. Fucose has also been used in the cosmetics, for skin moisturizing, skin regenerating, as an anti-aging agent and for preventing skin inflammation.
Fucose has been obtained from natural sources, synthesized chemically or enzymatically from monosaccharides and produced by microbe-assisted processes.
From natural sources, fucose containing oligosaccharides have been isolated from biomass, such as algae, by extraction, and then the oligosaccharides have been hydrolysed to provide complex mixtures of fucose and related sugars and derivatives. Recovery of the fucose has typically required sophisticated separation techniques such as chromatography with anion or cation exchange resins, dialysis, fractional crystallization, etc., depending on the nature of the accompanying sugars or sugar-related compounds (e.g. WO 2005/040430, P. Saari et. al. J. Liquid Chrom. Rel. Technol. 32, 2050 (2009)).
Chemical syntheses of fucose have involved chemical modifications of common monosaccharides like L-galactose, D-galactose, L-arabinose, D-glucose, D-mannose and L-rhamnose (see review: P. T. Vanhooren et al. J. Chem. Technol. Biotechnol. 74, 479 (1999), WO 2011/144213, WO 2013/046180, WO 2013/046181). Enzymatic syntheses of fucose and its analogs have been carried out from fuculose-6-phosphate using a multienzymatic system (see WO 97/15683).
Bacteria from Alcaligenes sp. have also been cultured to produce fucose-rich extracellular polysaccharides, from which the fucose has been released by acidic hydrolysis (see EP-A-102535). Similarly, a bacterial strain from the family Enterobacteriaceae has been found able to produce L-fucose containing polysaccharides under aerobic fermentation conditions, from which the fucose has been separated and isolated by acidic hydrolysis and many purification steps (see WO 2012/034996).
Fucosylated lactoses, particularly 2′-FL and DFL, have recently been synthesized by lengthy sequences of chemical process steps (see WO 2010/070616, WO 2010/115934, WO 2010/115935, Takeo et al. Carbohydr. Res, 141, 159 (1985), Fernandez-Mayoralas et al. Carbohydr. Res, 154, 93 (1986)). Lower cost ways of producing fucosylated lactoses have, however, been sought, such as by fermentation with transformed E. coli (see Drouillard et al. Angew. Chem, Int, Ed, 45, 1778 (2006); M. Randriantsoa: Synthèse microbiologique des antigènes glucidiques des groupes sanguins, Thèse de Doctorat soutenue le 30 Sep. 2008 a l'Université Joseph Fourier, Grenoble, France; WO 2010/070104; WO 2010/142305; WO 2012/097950WO2012/112777; Lee et al. Microb. Cell Fact, 11:48 (2012); Baumgärtner et al. Microb. Cell Fact. 12:40 (2013)).
However, better methods have continued to be sought for the low-cost manufacture of fucosylated lactoses which could be hydrolysed to produce fucose at low cost.